1. Field of the Invention
This invention relates to a plasma display panel, in particular a plasma display panel with high luminance and high contrast.
2. Description of the Related Art
For improving image quality of a plasma display panel, for example, JP-A 8-287834/1996 has disclosed a technique of forming a photoabsorption layer on the viewing side of the panel. FIG. 3 shows a schematic sectional view of a cell as an example of a plasma display panel of the prior art.
In a color panel, each fluorescence layer 9 is colored in R(red), G(green) and B(blue) corresponding to luminescent colors of individual cells. UV generated in a discharge space cell is radiated on the fluorescence layer 9 to emit colors assigned to individual fluorescence layers.
In addition, light observed in the viewing side includes external light besides emission light. It is light generated by reflection of incident light into the cell from the outside, on the fluorescence layer 9 and a dielectric layer 11. It may increase luminance of black display, leading to reduction of contrast ratio. To remove the external light, a photoabsorption layer 15 is formed.
The photoabsorption layer plays a role as a dielectric layer required in AC type drive, i.e., a drive procedure in which voltages with different polarities are alternately applied to a discharge cell for light emission. External light passes through the photoabsorption layer 15 twice, i.e., at incidence and reflection. On the other hand, since emission light passes once, reducing a transmission may allow contrast to be improved.
There has been disclosed, for example in JP-A 8-138559/1996, a technique for effectively taking emission light in which a wavelength-selective reflection film is formed on a rear side for effectively reflecting only emission light. Specifically, a wavelength-selective reflection film is formed on the rear side of the fluorescence layer to reflect emission light from the fluorescence layer to the rear side for effectively utilizing the emission light.
JP-As 3-190039/1991 and 3-246857/1991 have disclosed a technique in which a fluorescence layer is formed on the rear-substrate side and a technique in which a reflection film is further formed on the rear-substrate side.
One problem in the prior art is that a display luminance is reduced due to a photoabsorption layer for improving display contrast. Display luminance may vary depending on a transmission of the photoabsorption layer. A resulting display may be of high contrast and low luminance or of low contrast and high luminance.
An adequately high quality of image cannot be, therefore, displayed because a photoabsorption layer is formed on the viewing-side substrate and a reflectance of the fluorescence layer is high.